Preheat oven to 400 degrees F. Lightly coat six 2 1/2-inch muffin cups with nonstick cooking spray or line with paper bake cups and coat insides of paper cups with nonstick cooking spray; set aside.
In a medium bowl, stir together flour, oats, brown sugar, flax seed meal, baking powder, cinnamon, and salt. Make a well in the center of the flour mixture; set aside.
In a blender, combine banana, milk, egg, and oil. Cover and blend until smooth. Add banana mixture all at once to flour mixture; stir just until moistened (batter should be lumpy). Spoon batter into prepared muffin cups, filling each about three-fourths full.
Bake for 18 to 20 minutes or until lightly browned. Cool in muffin cups on a wire rack for 5 minutes. Remove from muffin cups. Serve warm.